java - 根据 android studio 编译器，数据库表不存在

Question

我收到此错误:

android.database.sqlite.SQLiteException: no such table: setting (code 1): , while compiling: SELECT * FROM setting

但我已经在我的 DatabaseHandler 文件中创建了表:

public class DatabaseHandler extends SQLiteOpenHelper {

    // Database Version
    private static final int DATABASE_VERSION = 1;

    // Database Name
    private static final String DATABASE_NAME = "database.db";

    //table name
    private static final String TABLE_DETAILS = "details";
    private static final String TABLE_FOOD = "food";
    private static final String TABLE_OLDDETAILS = "oldDetails";
    private static final String TABLE_SETTING = "setting";

    //Table Columns names
    private static final String KEY_ID = "id";
    private static final String KEY_NAME = "name";
    private static final String KEY_HEIGHT = "height";
    private static final String KEY_WEIGHT = "weight";
    private static final String KEY_CALORIES = "calories";
    private static final String KEY_DATE = "date";
    private static final String KEY_LEVEL = "level";
    private static final String KEY_DURATION = "duration";
    private static final String KEY_DAYS = "days";


    public DatabaseHandler(Context context) {
        super(context, DATABASE_NAME, null, DATABASE_VERSION);
    }

    // Creating Tables
    @Override
    public void onCreate(SQLiteDatabase db) {
        String CREATE_DETAILS_TABLE = "CREATE TABLE IF NOT EXISTS " + TABLE_DETAILS + "("
                + KEY_ID + " INTEGER PRIMARY KEY," +  KEY_HEIGHT + " REAL," + KEY_WEIGHT + " REAL " + ")";
        String CREATE_FOOD_TABLE = "CREATE TABLE IF NOT EXISTS " + TABLE_FOOD + "("
                + KEY_ID + " INTEGER PRIMARY KEY," + KEY_NAME + " TEXT," + KEY_CALORIES + " INTEGER " + ")";
        String CREATE_OLDDETAILS_TABLE = "CREATE TABLE IF NOT EXISTS " + TABLE_OLDDETAILS + "("
                + KEY_ID + " INTEGER PRIMARY KEY," + KEY_DATE + " TEXT," +  KEY_HEIGHT + " REAL," + KEY_WEIGHT + " REAL " + ")";
        String CREATE_SETTING_TABLE = "CREATE TABLE IF NOT EXISTS " + TABLE_SETTING + "("
                + KEY_ID + " INTEGER PRIMARY KEY," +  KEY_LEVEL + " INTEGER," + KEY_DURATION + " INTEGER," + KEY_DAYS + " INTEGER " + ")";

        db.execSQL(CREATE_OLDDETAILS_TABLE);
        db.execSQL(CREATE_DETAILS_TABLE);
        db.execSQL(CREATE_FOOD_TABLE);
        db.execSQL(CREATE_SETTING_TABLE);
    }

    // Upgrading database
    @Override
    public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
        // Drop older table if existed
        db.execSQL("DROP TABLE IF EXISTS " + TABLE_DETAILS);
        db.execSQL("DROP TABLE IF EXISTS " + TABLE_OLDDETAILS);
        db.execSQL("DROP TABLE IF EXISTS " + TABLE_FOOD);
        db.execSQL("DROP TABLE IF EXISTS " + TABLE_SETTING);

        // Create tables again
        onCreate(db);
    }
 public boolean addSetting(int level, int duration, int days) {
        SQLiteDatabase db = this.getWritableDatabase();

        ContentValues values = new ContentValues();
        values.put(KEY_ID, 1);
        values.put(KEY_LEVEL, level);
        values.put(KEY_DURATION, duration);
        values.put(KEY_DAYS, days);

        // Inserting Row
        long result = db.insert(TABLE_SETTING, null, values);
        if(result == -1){
            return false;
        }
        else{
            return true;
        }
    }
public boolean checkSetting(){
        SQLiteDatabase db = this.getWritableDatabase();
        String selectQuery = "SELECT * FROM " + TABLE_SETTING;
        Cursor cursor = db.rawQuery(selectQuery, null);
        Boolean rowExists;

        if (cursor.moveToFirst())
        {
            // DO SOMETHING WITH CURSOR
            rowExists = true;

        } else
        {
            // I AM EMPTY
            rowExists = false;
        }
        return rowExists;
    }
public setting getSetting() {
        String selectQuery = "SELECT * FROM " + TABLE_SETTING;
        SQLiteDatabase db = this.getWritableDatabase();
        Cursor cursor = db.rawQuery(selectQuery, null);
        if (cursor != null)
            cursor.moveToFirst();
        setting set = new setting(cursor.getInt(1), cursor.getInt(2), cursor.getInt(3));

        return set;
    }
public int updateSetting(setting set) {
        SQLiteDatabase db = this.getWritableDatabase();
        ContentValues values = new ContentValues();
        values.put(KEY_LEVEL, set.getLevel());
        values.put(KEY_DURATION, set.getDuration());
        values.put(KEY_DAYS, set.getDays());
        Log.d("UPDATE: ", "updated all");

        // updating row
        return db.update(TABLE_SETTING, values, KEY_ID + " = ?", new String[] { String.valueOf(1) });
    }

如您所见，有“CREATE IF NOT EXISTS”方法，我正在尝试创建它，尽管错误不断重复。

我试图在一个 fragment 中执行这个数据库代码，你可以看到 here到目前为止，这似乎不是问题所在，我认为主要是 DatabaseHandler。

如何正确创建表 SETTING 以便我可以从中进行选择？

Answer 1

您在应用程序已安装时更改了数据库结构，但 onCreate 只会执行一次，因此您有两个选项可以让您的更改反射(reflect)到数据库中

1.) 将数据库版本递增 1 以执行 onUpgrade 将更改应用到现有数据库

2.) 从手机上手动卸载应用程序以执行onCreate